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Original question:

SN74AVCH2T45 power-up sequence

SN74AVCH2T45: Power up sequence

Lacey Lin
Intellectual 2900 points
Part Number: SN74AVCH2T45

Hi team,

For the power up sequence, if I supply VCCB before VCCA.

According to the previous post, the DIR pin will stay low until the VCCA is up. Does it means if during power up, there is signal in port B, it will also transfer to port A?

In addition, after VCCA is up. Is there any possible to cause the device to be stuck and don't have any effect whenever we change the voltage level of the port A?

Lacey

Thanks a lot!

  • 0
    TI__Guru 56300 points
    Hi Lacey,

    The SN74AVCH2T45 supports Ioff, which means that the IO channels are in Hi-Z with Vcca / Vccb at 0V.
    During power up, the Hi-Z state is maintained, but the Ioff circuitry deactivates about ~0.5V. Above that, the device may be active with B to A transfer.
    There will be no device damage due to this power sequence though. Would the bus hold feature be used and what is the application?